Adaptive envelope tracking threshold

ABSTRACT

An apparatus of a transmitter and method are provided, the apparatus comprising a processor that calculates a supply voltage (SV) value (SVV) to provide as an SV for a power amplifier (PA) of the transmitter for transmissions during a transmission time slot (TS). When the SV&lt;an envelope tracking (ET) threshold (ETT), then the processor configures the PA to transmit a signal in an average power tracking (APT) mode that maintains the SV at the SVV during the TS. When the SV≥ETT, and an APT condition is met, then the processor configures the PA to transmit the signal in the APT mode. When the SV≥ETT, and the APT condition is not met, then the processor transmits by an adjustment to the SVV to track an amplitude modulation envelope during the TS in an ET mode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/475,996, filed Mar. 31, 2017, which is incorporated by referenceherein in its entirety.

TECHNICAL FIELD

The present disclosure relates to power conservation in transmitters andtransceivers, such as those used in mobile communication devices andbase stations.

BACKGROUND

Power conservation is a desirable attribute in a transceiver device,particularly a mobile or portable communication device, such as a cellphone, or a base transceiver station. Such devices may utilize anaverage power tracking (APT) mechanism or an envelope tracking (ET)mechanism. Cellular transmissions using protocols such as the Long-TermEvolution (LTE)-Advanced protocol (based on a 3GPP Release 10specification released in March of 2011 and 3GPP Release 13, 2016Update) may occur in time slots which, according to the LTE protocol,are 0.5 ms.

With the APT mechanism, a biasing voltage supplied to the poweramplifier (PA) is selected based on a desired signal quality (linearityand/or efficiency) specified by the communication standard and is fixedduring the time slot (but is changeable from slot-to-slot). This PAsupply voltage value is set by a DC-DC converter, which takes the DCvoltage supplied by a battery of the device and regulates it to adifferent value that may be used by the PA. The value is calculatedbased generally on a target output power level for that time slot. Forexample, if the target value (average power level) for sending the slotis 20 dBm, then a look-up table (LUT) may indicate that the DC-DCvoltage should be fixed at 2.7 V for that time slot.

For envelope tracking, a fast DC-DC converter is used so that the supplyvoltage to the PA is adjusted to track the amplitude modulation signal,which helps reduce the power. However, depending on the characteristicsof the output signal, use of ET is not always beneficial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram with output graph that illustrates an APTsystem or operation in an APT mode;

FIG. 1B is a block diagram with output graph that illustrates an ETsystem 100 (or operation in an ET mode);

FIG. 2A is a graph showing the spectrum for a case in which there aretwo clusters of six resource blocks (RBs) each, spaced by 5 MHz;

FIG. 2B is a graph showing the power versus time of the combined signal;

FIG. 2C is a graph similar to the one in FIG. 2A, but showing thespectrum for a case in which there are twelve RBs that are contiguous;

FIG. 2D is the same graph as FIG. 2C, but using a larger scale;

FIG. 2E is a graph similar to the one in FIG. 2B for the case of thetwelve contiguous RBs;

FIG. 3 is a block diagram illustrating an example of a transmitter 300that may be utilized as described herein;

FIG. 4 is a graph that illustrates a linearity improvement given by ET,showing how the amplitude-to-amplitude modulation (AM/AM) characteristicof the PA can be engineered by selecting a correct correspondencebetween the envelope of the RF signal and the PA supply voltage;

FIG. 5 is a flowchart that illustrates a high level process that may beused; and

FIG. 6 is a block diagram illustrating a machine that may be a computeron which various processes described herein may be performed, inaccordance with some aspects of the inventive subject matter.

DETAILED DESCRIPTION

The following is a detailed description of various configurationsdepicted in the accompanying drawings. However, the amount of detailoffered is not intended to limit anticipated variations of the describedconfigurations; to the contrary, the claims and detailed description areto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the present teachings as defined by the claims.The detailed descriptions below are designed to make such configurationsunderstandable to a person having ordinary skill in the art.

FIG. 1A is a block diagram with output graph that illustrates an APTsystem 100′ (or operation in an APT mode) in which a transceiver 110′provides a modulated radio frequency (RF) signal 120 to a PA 130. Thetransceiver 110′ also provides a constant control voltage V_(CTRL) 140′to the DC-DC converter 150′, which, in turn, provides a constant (for atime slot) supply voltage V_(CC) 160′ to the PA 130. The supply voltageV_(CC) 160′ mainly depends on a target output level, but may becorrected for frequency, temperature, and modulation type. With V_(CC)160′ constant, it can be seen that the resultant V_(OUT) 170 waveformcreates a significant amount of lost energy that is dissipated as heat185 (inefficiency) when the RF envelope 180 amplitude is less than thesupply voltage V_(CC) 160′.

FIG. 1B is a block diagram with output graph that illustrates an ETsystem 100 (or operation in an ET mode). In an ET mode, the controlpower V_(CC) 160 of the PA 130 follows the modulated amplitude 180faster than with the DC-DC converter operating in the APT mode, andsupplies a high voltage to the PA 130 when the amplitude modulationrequires a transmit signal with a high amplitude (beneficial for highpower limits). To illustrate, in this system 100, the transceiver 110provides a modulated RF signal 120 to the PA 130. However, in thisconfiguration, it provides a variable control voltage V_(CTRL). 140 toan envelope tracking (ET) modulator 150, which, in turn, provides avariable/modulated supply voltage V_(CC) 160 to the PA 130. With V_(CC)160 tracking the RF envelope 180, no power is lost as it was in thedesign shown in FIG. 1A. The ET modulator 150 may be a fast DC-DCconverter whose output voltage varies over time as a function of theamplitude modulation of the transceiver 110. It is most beneficial ifthe PA 130 can be operated as close as possible to saturation during themodulation peaks and then to lower the voltage when the instantaneousamplitude signal is low, thereby boosting the PA efficiency. Bymodulating the biasing voltage dynamically depending on the actual valueof the signal's envelope, it may be possible to improve the averageefficiency.

LTE carrier aggregation (CA) makes it possible to utilize more than onecarrier to increase an overall transmission bandwidth. However, whendealing with LTE CA signals, a situation may arise in which the LTEmodulation is constituted by disjoined resource blocks (that is, datablocks in discontinuous frequency bands) (in transmit carrieraggregation (TX CA) and multi-cluster transmissions). In suchcircumstances, the amplitude signal 180, which needs to be tracked bythe DC-DC converter (the ET modulator) 150 has a very high frequencycontent and periodicity at the tracker's 150 output 160, and hence, atthe antenna, undesired spurs may arise as a consequence of the DC-DCnon-linearities. This is illustrated in the following graphs.

FIG. 2A is a graph showing the spectrum for a case in which there aretwo clusters of six RBs each, spaced by 5 MHz FIG. 2B is a graph showingthe power versus time of the combined signal.

FIG. 2C is a graph similar to the one in FIG. 2A, but showing thespectrum for a case in which there are twelve RBs that are contiguous.FIG. 2D is the same graph as FIG. 2C, but using a larger scale. FIG. 2Eis a graph similar to the one in FIG. 2B for the case of the twelvecontiguous RBs. For the first case in which the clusters of RBs arespaced by 5 MHz, the massive periodicity presents a significantchallenge for an envelope tracking system.

FIG. 3 is a block diagram illustrating an exemplary example of atransmitter or a transceiver 300 that may be utilized as describedherein. The components are generally broken down into an ET path(components in the ET digital 320 and ET analog 350 blocks) and atransmit (TX) path (components in the TX digital 360 and TX analog 380blocks). The transmitter receives the baseband (BB) signal 302 which isshared between the ET and TX paths. The ET path is used to generate themodulated supply voltage used at the PA 130. The BB signal 302 isbranched off after a frequency limiter 305 via a multipurposemultiplexing (MULTI MUX-DLY) circuit 310. This allows an introduction ofpart of a compensation delay in either the ET or the TX path. Afractional delay block 322 follows for finer time alignment.

ET operation is only practical when the power consumed in the ET path islower than the power saved in the PA 130 when the ET mode is used. Byway of example, it may be determined that with a PA having a maximumpower level of 24 dBm, the ET mode is efficient only for power levels ator above 14 dBm (that is, in the upper 10 dB of the power range). Whenthe power level is below this, then it is more efficient to transmit inthe APT mode.

When the power is in this high power range, the transmitter or thetransceiver 300 may be operated with a closed loop power regulationwhich affects the amplitude of an AM signal in the TX-AM 370 path.Consequently, in order not to miss an alignment between the signal'senvelope at the input of the PA 130 and the supply's envelope, aninterface is needed in the ET path which mimics the amplitude scalinginduced by the PCL on the TX-AM 370. This is provided by a multiplier M1324.

In order to target the needed noise limits at the PA output 170 to theantenna port (FE), a clean supply's envelope is needed. This turns outto benefit from a relatively high sampling frequency for the envelope ofthe BB signal 302. Therefore, an interpolation block TN CIC 326 isprovided which interpolates the I and Q signals before the calculationof their amplitude. The interpolation 326 takes place just before thecoordinate rotation digital computer (CORDIC) |⋅| 328 calculations (themost convenient place). The interpolation 326 takes place after thedelay 322 and the scaling 324 to slow down the sampling rate and savecurrent, and before the CORDIC 328 to simplify the interpolationfiltering, due to the bandwidth of the I and Q signals being lower thanthat of the envelope.

A nonlinear transformation maps corresponding values of the signalenvelope to the PA supply 160. This is realized due to the look-up table(LUT) 330 following the CORDIC 328. After the nonlinear transformationis provided by the LUT 330, the linear correction of the amplitude andphase distortions introduced by the following blocks (group delayequalization (EQ-GD) 332 and amplitude equalization (EQ-AM) 334) can beperformed. It may be beneficial to keep the EQ-GD 332 and the EQ-AM 334independent because it increases flexibility, and it allows a dedicatedcorrection of the group delay on its own (constancy of the group delaymay be a limiting requirement for ET).

The following analogue parts, such as the power amplifier digital toanalog converter (PADAC) 352, may be affected during operation byundesired effects like a drift of the gain with temperature and/or a DCoffset. In order to compensate for these effects, which are completelyindependent from elements that affect the TX chain, a multiplier M2 336and an adder S2 338 may be provided in the ET chain.

The clock concept of the transceiver provides for a modulated clock toboth the RFDAC (not shown) and the PADAC 352 (which is a digitallycontrolled oscillator (DCO) modulated by the phase modulator (PM)according to the polar architecture of the TX). All of the digitalblocks may be provided with an un-modulated clock. Consequently, afractional sample rate converter (FSRC-ET) 340 may be provided thatcorrectly realizes the signal's conversion in between the digital andthe analogue world. The PADAC 352 converts the digital information to ananalog voltage signal which is then transduced to a modulated supply bythe following DC-DC converter 150.

The ET operation parameters (compression point, tracker's settings, andPA biasing) may be modified in order to pass a linearity test inmulti-cluster or carrier-aggregation cases, but the result is anoptimization between linearity and current consumption. The switchingmechanisms described herein helps to ensure linearity in difficultmulti-cluster and TX carrier aggregation cases without affecting theperformance in ET operation at maximum output power, which is a keyperformance indicator (KPI).

FIG. 4 is a graph 400 that illustrates a linearity improvement given byET, showing how the amplitude-to-amplitude modulation (AM/AM)characteristic of the PA can be engineered by selecting a correctcorrespondence between the envelope of the RF signal and the PA supplyvoltage. A straight AM/AM characteristic 405 of the PA operated in ETmode means that there is a constant gain provided by the PA at allinstantaneous amplitudes of the signal's envelope, which defines the“ISO-gain” curve (the ISO-gain being the gain of the PA which does notchange in response to variations in V_(CC) and V_(IN)). The family ofcurved lines represent the AM/AM characteristics 410 when the PA isoperated with a fixed V_(CC), (that is, in APT mode) with the topcharacteristic 415 being a high V_(CC), and the bottom characteristic420 being a low V_(CC).

As can be seen in FIG. 4, at a given PA input signal P_(IN) 120, theoutput signal P_(OUT) 170 is the same 430 for operation in the ET modeand some minimum fixed V_(CC). However, with the V_(CC) set at a higherfixed voltage, for the same input signal P_(IN), the output signalP_(OUT) is higher 435. In any case, by operating in the ET mode, alinear output for the input at P_(IN1) to P_(IN2) (between points 430and 445) may be achieved, whereas operation in the APT mode at anyillustrated fixed voltage level given the same input at P_(IN1) toP_(IN2) results in non-linearity. In other words, when operating at thehigher end of input signal PIN, the non-linear characteristics (e.g.,between points 440 and 445) of the fixed voltage mode become morepronounced over the linear operation of the ET mode of operation (e.g.,between points 430 and 445). As can be seen from FIG. 4, when operatingin the lower input power regions, the linearity for operating in the APTmode at a fixed voltage may be acceptable.

According to an exemplary device described herein, the transmitter orthe transceiver may be switched to operate in either the ET mode or theAPT mode according to particular criteria that may result in beneficialoperation of the device. In certain situations, the transceiver may beswitched to use the ET mode or the APT mode based upon the target powerlevels of a particular transmission. However, some signals arechallenging to handle in ET mode because of the nature of their ETregions, and may be difficult to deal with. Such a situation is presentwith LTE CA signals when the LTE modulation has multi-clustertransmissions constituted by disjointed resource blocks. As illustratedabove, this creates very fast up and down transitions in the timedomain, making ET difficult to do effectively. Therefore, when thissituation is detected, switching to the ET mode or remaining in the ETmode is avoided, or, put differently, switching to the APT mode orremaining in the APT mode is undertaken. Thus, the system 100 isswitchable between operating in the APT mode and an ET mode based on athreshold that is a function of the distribution of the allocated RBs(considering both multi-cluster and TX CA cases). The switching maycause the system 100 to revert to or stay in the APT mode whenever it isoperating in the multi-cluster mode, or when the spacing between theclusters is higher than a specified threshold. The loss in efficiencydue to reverting to the APT mode may be balanced by a better linearityin operating the PA 130.

Put another way, although the switching from the APT mode to the ET modeor maintaining the ET mode may be performed if the target power (TP)value is greater than some predefined envelope tracking threshold (ETT)value (and switching back to the APT mode or maintaining the APT mode,if the converse is true), further criteria for determining whether toswitch/maintain the ET mode may be utilized.

FIG. 5 is a flowchart that illustrates a high level process 500 that maybe used.

In operation S510, the transmission parameters, including an averagetransmission power for the time slot, are determined. In operation S520,a determination is made to see if a first condition is met. As shown inFIG. 5, this first condition is whether the average transmission poweris less than the ETT. This threshold may relate to an amount of powerconsumed by the ET circuitry to implement the ET mode. As discussedabove, if the power consumed by the circuitry is greater than the powersavings by running in ET mode and/or is less than the ETT (S520:Y), thenthe device, in operation S530, either switches to or remains in the APTmode for transmitting the data in the time slot in operation S560.

Otherwise (S520:N), a further determination is made to see if a secondcondition is met. In operation S540, this condition is genericallydescribed as being whether the ET mode is not valid or appropriate underthe circumstances by applying further criteria. These further criteriacan include the following factors: a) a number of allocated RBs for thetransmission; b) a distance between the RBs, and c) a power ratiobetween disjoined clusters. These factors can be considered individuallyor can be combined in any way. Furthermore, the factors that are appliedcan be taken as being threshold-based, or could utilize a weightedfactor analysis.

In a threshold case, and considering the factors individually, forfactor (a), an RB count (RBC) threshold (RBCT) may be utilized, whereinif a number of RBs used in the transmission is below the RB countthreshold, then the ET mode can be used as long as the other powerrequirements are met; otherwise, the APT mode is used. For factor (b),an RB distance (RBD) threshold (RBDT) may be utilized, such that if amaximum frequency distance is below the RB distance, then the ET modecan be used as long as the other power requirements are met; otherwise,the APT mode is used. For factor (c), a power ratio between disjoinedclusters (CPR) threshold (CPRT) may be utilized, such that if a powerdifference between clusters is not exceeded, then the ET mode can beused as long as the other power requirements are met; otherwise, the APTmode is used. The factor tests may be combined in a number of ways tosee if the second condition is met. Any or all of the following testsmay be utilized as the second condition (further criteria) to determinewhether to stay in or switch to the APT mode:

1) if (RBC>RBCT)

2) if (RBD>RBDT)

3) if (CPR>CPRT)

In one implementation, these tests are connected by OR logic, meaningthat if any one of them is true, the transmitter switches to or remainsin the APT mode, but if they are all false, then the transmitterswitches to or remains in the ET mode.

In a weighted factor case, appropriate weighting values (w₁-w₃) could beapplied to factor values (a)-(c). Thus some overall ET mode threshold(EMT) value could be defined and the following test as the further testcould be used to determine whether to stay in or switch to the ET mode:

if(EMT≤w ₁RBC+w ₂RBD+w ₃CPR)

The weightings could be chosen to compensate for the particular units ofthe factors and empirical determinations of values that yield the mostdesirable results.

In a hybrid configuration, both threshold values and weightings could beused. In one configuration, the threshold values may take precedenceover the weighting values, meaning that a threshold condition must bemet before weighted factors can be considered. In another configuration,the weighting values may take precedence over the threshold values,meaning that a weighted factor can trump a factor not meeting athreshold if its value is large enough.

If the further criteria in operation S540 indicate that the ET mode isnot valid (S540:Y), then the device switches to or remains in the APTmode S530. Otherwise (S540:N) the device switches to or remains in theET mode S550 and proceeds to transmit the data in the time slot S560.

To describe some configurations in greater detail, reference is made toexamples of hardware structures and interconnections usable in thedesigns of the present disclosure.

FIG. 6 is a block diagram illustrating a machine that may be a computeron which various processes described herein may be performed. Themachine (e.g., computer system, communications device) 600 may include ahardware processor 602 (e.g., a central processing unit (CPU), agraphics processing unit (GPU), a hardware processor core, or anycombination thereof), a main memory 604 and a static memory 606, some orall of which may communicate with each other via an interlink (e.g.,bus) 608. The machine 600 may further include a display unit 610, analphanumeric input device 612 (e.g., a keyboard), and a user interface(UI) navigation device 614 (e.g., a mouse). In an example describedherein, the display unit 610, input device 612 and UI navigation device614 may be a touch screen display. The machine 600 may additionallyinclude a storage device (e.g., drive unit) 616, a signal generationdevice 618 (e.g., a speaker), a network interface device 620, and one ormore sensors 621, such as a global positioning system (GPS) sensor,compass, accelerometer, or other sensor. The machine 600 may include anoutput controller 628, such as a serial (e.g., universal serial bus(USB)), parallel, or other wired or wireless (e.g., infrared (IR), nearfield communication (NFC), etc.) controller connection to communicate orcontrol one or more peripheral devices (e.g., a printer, card reader,etc.).

The storage device 616 may include a machine readable medium 622 onwhich is stored one or more sets of data structures or instructions 624(e.g., software) embodying or utilized by any one or more of thetechniques or functions described herein. The instructions 624 may alsoreside, completely or at least partially, within the main memory 604,within static memory 606, or within the hardware processor 602 duringexecution thereof by the machine 600. In an example, one or anycombination of the hardware processor 602, the main memory 604, thestatic memory 606, or the storage device 616 may constitute machinereadable media.

While the machine readable medium 622 is illustrated as a single medium,the term “machine readable medium” may include a single medium ormultiple media (e.g., a centralized or distributed database, and/orassociated caches and servers) configured to store the one or moreinstructions 624.

The term “machine readable medium” may include any medium that iscapable of storing, encoding, or carrying instructions for execution bythe machine 600 and that cause the machine 600 to perform any one ormore of the techniques of the present disclosure, or that is capable ofstoring, encoding or carrying data structures used by or associated withsuch instructions. Non-limiting machine readable medium examples mayinclude solid-state memories, and optical and magnetic media. Specificexamples of machine readable media may include: non-volatile memory,such as semiconductor memory devices (e.g., Electrically ProgrammableRead-Only Memory (EPROM), Electrically Erasable Programmable Read-OnlyMemory (EEPROM)) and flash memory devices; magnetic disks, such asinternal hard disks and removable disks; magneto-optical disks; RandomAccess Memory (RAM); Solid State Drives (SSD); and CD-ROM and DVD-ROMdisks. In some examples, machine readable media may includenon-transitory machine readable media. In some examples, machinereadable media may include machine readable media that is not atransitory propagating signal.

The instructions 624 may further be transmitted or received over thecommunications network 626 using a transmission medium via the networkinterface device 620. The term “transmission medium” is defined hereinto include any medium that is capable of storing, encoding, or carryinginstructions for execution by the machine, and includes digital oranalog communications signals or other medium to facilitatecommunication of such software.

The machine 600 may communicate with one or more other machines 600utilizing any one of a number of transfer protocols (e.g., frame relay,internet protocol (IP), transmission control protocol (TCP), userdatagram protocol (UDP), hypertext transfer protocol (HTTP), etc.).Example communication networks may include a local area network (LAN), awide area network (WAN), a packet data network (e.g., the Internet),mobile telephone networks (e.g., cellular networks), Plain Old Telephone(POTS) networks, and wireless data networks (e.g., Institute ofElectrical and Electronics Engineers (IEEE) 802.11 family of standardsknown as Wi-Fi®, WiGig®, IEEE 802.16 family of standards known asWiMax®), IEEE 802.15.4 family of standards, a Long Term Evolution (LTE)family of standards, a Universal Mobile Telecommunications System (UMTS)family of standards, peer-to-peer (P2P) networks, virtual privatenetworks (VPN), or any other way of transferring data between machines600. In an example, the network interface device 620 may include one ormore physical jacks (e.g., Ethernet, coaxial, or phone jacks) or one ormore antennas to connect to the communications network 626.

In an example, the network interface device 620 may include a pluralityof antennas to wirelessly communicate using at least one of single-inputmultiple-output (SIMO), multiple-input multiple-output (MIMO), ormultiple-input single-output (MISO) techniques. In some examples, thenetwork interface device 620 may wirelessly communicate using MultipleUser MIMO techniques.

A wide variety of computing devices may constitute a machine 600, asdescribed herein. The following list includes a variety of devices thatmay fit the definition of a machine 600: a personal data assistant(PDA), a cellular telephone, including a smartphone, a tablet computingdevice, a laptop computer, a desktop computer, a workstation, a servercomputer, a mainframe computer, and the like.

By applying the techniques described herein, it is possible to improve akey performance indicator (KPI) of a mobile unit (namely, the amount ofcurrent/power the transmitter consumes at a particular antenna powerlevel) that is capable of improving efficiency by being switchablebetween operation in the APT mode or the ET mode, but remains in the APTmode under operational situations that otherwise might suggest switchingto an ET mode of operation.

For the purposes of promoting an understanding of the principles of thisdisclosure, reference has been made to the various configurationsillustrated in the drawings, and specific language has been used todescribe these configurations. However, no limitation of the scope ofthe inventive subject matter is intended by this specific language, andthe inventive subject matter should be construed to encompass allembodiments and configurations that would normally occur to one ofordinary skill in the art. The configurations herein may be described interms of functional block components and various processing steps. Suchfunctional blocks may be realized by any number of components thatperform the specified functions. The particular implementations shownand described herein are illustrative examples and are not intended tootherwise limit the scope of the inventive subject matter in any way.The connecting lines, or connectors shown in the various figurespresented may, in some instances, be intended to represent examplefunctional relationships and/or physical or logical couplings betweenthe various elements. However, many alternative or additional functionalrelationships, physical connections or logical connections may bepresent in a practical device. Moreover, no item or component isessential unless the element is specifically described as “essential” or“critical”. Numerous modifications and adaptations will be readilyapparent to those skilled in this art.

EXAMPLES

Example 1 is an apparatus of a transmitter, the apparatus comprising:memory or a memory circuitry; and processing circuitry, configured to:calculate a supply voltage value to provide as a supply voltage for apower amplifier (PA) of the transmitter for transmissions during atransmission time slot (TS); when the supply voltage is less than anenvelope tracking threshold (ETT), then configure the PA to transmit asignal in an average power tracking (APT) mode that maintains the supplyvoltage at the supply voltage value during the TS; when the supplyvoltage is greater than or equal to the ETT, and an APT condition ismet, then configure the PA to transmit the signal in the APT mode; andwhen the supply voltage is greater than or equal to the ETT, and the APTcondition is not met, then transmit by an adjustment to the supplyvoltage value to track an amplitude modulation envelope during the TS inan envelope tracking (ET) mode.

In Example 2, the subject matter of Example 1 optionally includeswherein the APT condition relates to a factor comprising one of: aresource block count (RBC), a resource block distance (RBD), or a powerratio between disjoined clusters (CPR).

In Example 3, the subject matter of Example 2 optionally includeswherein: factors of the APT condition comprise a threshold valuecomprising one of: a resource block count threshold (RBCT), a resourceblock distance threshold (RBDT), and a power ratio between disjoinedclusters threshold (CPRT); and the APT condition is defined as: when theresource block count is greater than the resource block count threshold,or when the resource block distance is greater than the resource blockdistance threshold, or when the power ratio between disjoined clustersis greater than the power ratio between disjoined clusters threshold.

In Example 4, the subject matter of any one or more of Examples 2-3optionally include wherein: the processing circuitry is furtherconfigured to: apply a weighting value to at least one of the factors;and the APT condition is defined as: when an ET threshold value is lessthan or equal to a sum of a first weighting factor times the resourceblock count, a second weighting factor times the resource blockdistance, and a third weighting factor times the power ratio betweendisjoined clusters.

In Example 5, the subject matter of any one or more of Examples 1-4optionally include the power amplifier; and a DC-DC converter connectedto a voltage supply of the power amplifier.

In Example 6, the subject matter of any one or more of Examples 1-5optionally include wherein the transmitter device operates according toa Long-Term Evolution (LTE)-Advanced protocol.

Example 7 is a method for transmitting data from a transmitter or atransmitter device, comprising: calculating a supply voltage value toprovide as a supply voltage for a power amplifier (PA) of thetransmitter for a transmission time slot (TS); when the supply voltageis less than an envelope tracking threshold (ETT), then transmitting asignal using the PA while maintaining the supply voltage at the supplyvoltage value during the TS in an average power tracking (APT) mode;when the supply voltage is greater than or equal to the ETT, and an APTcondition is met, then transmitting the signal in the APT mode; and whenthe supply voltage is greater than or equal to the ETT and the APTcondition is not met, then performing the transmitting by adjusting thesupply voltage value to track an amplitude modulation envelope duringthe TS in an envelope tracking (ET) mode.

In Example 8, the subject matter of Example 7 optionally includeswherein the APT condition relates to a factor comprising one of: aresource block count (RBC), a resource block distance (RBD), or a powerratio between disjoined clusters (CPR).

In Example 9, the subject matter of Example 8 optionally includeswherein the APT condition factors comprise a threshold value comprisingone of: a resource block count threshold (RBCT), a resource blockdistance threshold (RBDT), and a power ratio between disjoined clustersthreshold (CPRT).

In Example 10, the subject matter of Example 9 optionally includeswherein the APT condition is defined as: when the resource block countis greater than the resource block count threshold, or when the resourceblock distance is greater than the resource block distance threshold, orwhen the power ratio between disjoined clusters is greater than thepower ratio between disjoined clusters threshold.

In Example 11, the subject matter of any one or more of Examples 8-10optionally include applying a weighting value to at least one of thefactors.

In Example 12, the subject matter of Example 11 optionally includeswherein the APT condition is defined as: when an ET threshold value isless than or equal to a sum of a first weighting factor times theresource block count, a second weighting factor times the resource blockdistance, and a third weighting factor times the power ratio betweendisjoined clusters.

In Example 13, the subject matter of any one or more of Examples 8-12optionally include wherein the APT condition factors comprise: athreshold value comprising one of: a resource block count threshold(RBCT), a resource block distance threshold (RBDT), or a power ratiobetween disjoined clusters threshold (CPRT); and a weighting value forapplying to at least one of the factors.

In Example 14, the subject matter of Example 13 optionally includesusing a factor with the threshold value to take precedence over a factorwith the weighting value.

In Example 15, the subject matter of any one or more of Examples 13-14optionally include using a factor with the weighting value to takeprecedence over a factor with the threshold value.

In Example 16, the subject matter of any one or more of Examples 7-15optionally include switching from the APT mode to the ET mode for thetransmitting when performing the transmitting in the ET mode; andswitching from the ET mode to the APT mode for the transmitting whenperforming the transmitting in the APT mode.

In Example 17, the subject matter of any one or more of Examples 7-16optionally include wherein the transmitter device operates according toa Long-Term Evolution (LTE)-Advanced protocol.

In Example 18, the subject matter of any one or more of Examples 7-17optionally include providing the supply voltage with a DC-DC converter.

Example 19 is a computer program product comprising one or more computerreadable storage media comprising computer-executable instructionsoperable to, when executed by processing circuitry of a device,configure the station to perform any of the methods of Examples 7-18.

Example 20 is a computer program product comprising one or more tangiblecomputer readable non-transitory storage media comprisingcomputer-executable instructions operable to, when executed byprocessing circuitry of a device, configure the device to: calculate asupply voltage value to provide as a supply voltage for a poweramplifier (PA) of the transmitter for a transmission time slot (TS);when the supply voltage is less than an envelope tracking threshold(ETT), then configure the PA to transmit a signal in an average powertracking (APT) mode that maintains the supply voltage at the supplyvoltage value during the TS; when the supply voltage is greater than orequal to the ETT, and an APT condition is met, then configure the PA totransmit the signal in the APT mode; and when the supply voltage isgreater than or equal to the ETT, and the APT condition is not met, thentransmit by an adjustment to the supply voltage value to track anamplitude modulation envelope during the TS in an envelope tracking (ET)mode.

In Example 21, the subject matter of Example 20 optionally includeswherein the APT condition relates to a factor comprising one of: aresource block count (RBC), a resource block distance (RBD), or a powerratio between disjoined clusters (CPR).

Example 22 is a system comprising means to perform any of the methods ofExamples 7-18.

Example 23 is an apparatus for transmitting data from a transmitterdevice, comprising: means for calculating a supply voltage value toprovide as a supply voltage for a power amplifier (PA) of thetransmitter for a transmission time slot (TS); means for, when thesupply voltage is less than an envelope tracking threshold (ETT),transmitting a signal using the PA while maintaining the supply voltageat the supply voltage value during the TS in an average power tracking(APT) mode; means for, when the supply voltage is greater than or equalto the ETT, and an APT condition is met, transmitting the signal in theAPT mode; and means for, when the supply voltage is greater than orequal to the ETT and the APT condition is not met, performing thetransmitting by adjusting the supply voltage value to track an amplitudemodulation envelope during the TS in an envelope tracking (ET) mode.

In Example 24, the subject matter of Example 23 optionally includeswherein the APT condition relates to a factor comprising one of: aresource block count (RBC), a resource block distance (RBD), or a powerratio between disjoined clusters (CPR).

In Example 25, the subject matter of Example 24 optionally includeswherein the APT condition factors comprise a threshold value comprisingone of: a resource block count threshold (RBCT), a resource blockdistance threshold (RBDT), and a power ratio between disjoined clustersthreshold (CPRT).

In Example 26, the subject matter of Example 25 optionally includeswherein the APT condition is defined as: when the resource block countis greater than the resource block count threshold, when the resourceblock distance is greater than the resource block distance threshold, orwhen the power ratio between disjoined clusters is greater than thepower ratio between disjoined clusters threshold.

In Example 27, the subject matter of any one or more of Examples 24-26optionally include means for applying a weighting value to at least oneof the factors.

In Example 28, the subject matter of Example 27 optionally includeswherein the APT condition is defined as: when an ET threshold value isless than or equal to a sum of a first weighting factor times theresource block count, a second weighting factor times the resource blockdistance, and a third weighting factor times the power ratio betweendisjoined clusters.

In Example 29, the subject matter of any one or more of Examples 24-28optionally include wherein the APT condition factors comprise: athreshold value comprising one of: a resource block count threshold(RBCT), a resource block distance threshold (RBDT), or a power ratiobetween disjoined clusters threshold (CPRT); and a weighting value forapplying to at least one of the factors.

In Example 30, the subject matter of Example 29 optionally includesmeans for using a factor with the threshold value to take precedenceover a factor with the weighting value.

In Example 31, the subject matter of any one or more of Examples 29-30optionally include means for using a factor with the weighting value totake precedence over a factor with the threshold value.

In Example 32, the subject matter of any one or more of Examples 23-31optionally include means for switching from the APT mode to the ET modefor the transmitting when performing the transmitting in the ET mode;and means for switching from the ET mode to the APT mode for thetransmitting when performing the transmitting in the APT mode.

In Example 33, the subject matter of any one or more of Examples 23-32optionally include wherein the transmitter device operates according toa Long-Term Evolution (LTE)-Advanced protocol.

In Example 34, the subject matter of any one or more of Examples 23-33optionally include providing the supply voltage with a DC-DC converter.

1. (canceled)
 2. An apparatus comprising: envelope tracking (ET)circuitry configured to generate an output voltage during a transmissiontime slot (TS), the output voltage generated based on in-phase (I) andquadrature (Q) signals corresponding to an input signal, and the outputvoltage being adjusted relative to an amplitude-modulated signalcorresponding to the input signal when a target output power of theapparatus is greater than or equal to an ET threshold (ETT); andmodulator circuitry coupled to the ET circuitry and configured tomodulate the output voltage.
 3. The apparatus of claim 2, wherein theETT is within a predefined number of decibels of an upper limit of a PApower range.
 4. The apparatus of claim 2, wherein the ET circuitrycontrols the output voltage only when an average power tracking (APT)condition is not met.
 5. The apparatus of claim 4, wherein the APTcondition relates to one of: a resource block count (RBC), a resourceblock distance (RBD), or a power ratio between disjoined clusters (CPR).6. The apparatus of claim 5, wherein the APT condition relates to athreshold value comprising one of a resource block count threshold(RBCT), a resource block distance threshold (RBDT), and a power ratiobetween disjoined clusters threshold (CPRT).
 7. The apparatus of claim6, wherein the APT condition is defined as at least one of: when theresource block count is smaller than the resource block count threshold;when the resource block distance is greater than the resource blockdistance threshold; or when the power ratio between disjoined clustersis greater than the power ratio between disjoined clusters threshold. 8.The apparatus of claim 2, wherein the modulator circuitry includes adirect current (DC)-to-DC (DC-DC) converter.
 9. The apparatus of claim2, further comprising a memory, wherein the memory is configured tostore a look up table (LUT) that maps values of a signal envelope to theoutput voltage.
 10. An apparatus comprising: memory; and controlcircuitry configured to determine a supply voltage value to provide as asupply voltage for a power amplifier (PA) during a transmission timeslot (TS); and when the supply voltage value is less than an envelopetracking (ET) threshold, provide a control signal to instruct the PA totransmit a signal in an average power tracking (APT) mode that maintainsthe supply voltage at the supply voltage value during the TS.
 11. Theapparatus of claim 10, wherein the control circuitry is furtherconfigured to determine whether an APT condition is met, and wherein theAPT condition relates to a factor comprising one of: a resource blockcount (RBC), a resource block distance (RBD), or a power ratio betweendisjoined clusters (CPR).
 12. The apparatus of claim 10, wherein, whenthe APT condition is not met and the supply voltage is greater than orequal to the ET threshold, the control circuit is configured to providethe control signal to ET circuitry to instruct the ET circuitry togenerate an output voltage during the TS such that the output voltage isadjusted relative to an amplitude-modulated signal.
 13. The apparatus ofclaim 10, wherein the control circuitry is included in one oftransceiver circuitry and baseband circuitry.
 14. The apparatus of claim10, wherein the ET threshold is within a predefined number of decibelsof an upper limit of a PA power range.
 15. The apparatus of claim 11,wherein the APT condition relates to a threshold value comprising one ofa resource block count threshold (RBCT), a resource block distancethreshold (RBDT), and a power ratio between disjoined clusters threshold(CPRT).
 16. The apparatus of claim 15, wherein the APT condition isdefined as at least one of: when the resource block count is smallerthan the resource block count threshold; when the resource blockdistance is greater than the resource block distance threshold; or whenthe power ratio between disjoined clusters is greater than the powerratio between disjoined clusters threshold.
 17. A device comprising:envelope tracking (ET) circuitry configured to generate an outputvoltage during a transmission time slot (TS), the output voltagegenerated based on in-phase (I) and quadrature (O) signals correspondingto an input signal, and the output voltage being adjusted relative to anamplitude-modulated signal corresponding to the input signal when atarget output power of the device is greater than or equal to an ETthreshold (ETT); modulator circuitry coupled to the ET circuitry andconfigured to modulate the output voltage; and two or more antennasconfigured to transmit an output signal amplified based on the outputvoltage.
 18. The device of claim 17, wherein the ETT is within apredefined number of decibels of an upper limit of a PA power range. 19.The device of claim 17, wherein the ET circuitry controls the outputvoltage only when an average power tracking (APT) condition is not met,and wherein the APT condition relates to one of: a resource block count(RBC), a resource block distance (RBD), or a power ratio betweendisjoined clusters (CPR).
 20. The device of claim 19, wherein the APTcondition relates to a threshold value comprising one of a resourceblock count threshold (RBCT), a resource block distance threshold(RBDT), and a power ratio between disjoined clusters threshold (CPRT).21. The device of claim 17, further comprising a power amplifierconfigured to receive one of an output of the modulator circuitry or,when the target output power of the device is less than the ETT, acontrol signal instructing the power amplifier to operate in an averagepower tracking (APT) mode when amplifying the output signal.